In recent years, studies have been in progress for the practical and widespread use of safe driver assistance wireless systems by utilizing ITS (Intelligent Transport System). In such safe driver assistance wireless systems, in order to alert drivers in vehicles to avoid accidents, vehicle position information and other information are transmitted and received between two or more in-vehicle terminal devices mounted on vehicles via vehicle-vehicle communication and are also transmitted and received between roadside devices provided in roadside and in-vehicle terminal devices via roadside-vehicle communication.
In recent years, pedestrian-vehicle communication technologies have been presented in which a pedestrian terminal device carried by a pedestrian communicates directly with in-vehicle terminal devices in order to prevent pedestrian accidents. Since, in this pedestrian-vehicle communication, direct communication between a pedestrian terminal device and an in-vehicle terminal device enables alerts to be provided to both the pedestrian and the vehicle drivers at an appropriate time, this technology is expected to significantly prevent traffic accidents involving pedestrians.
In such a pedestrian-vehicle communication, pedestrian information including pedestrian position information is transmitted from a pedestrian terminal device carried by a pedestrian to an in-vehicle terminal device mounted on a vehicle, and upon receiving the pedestrian information, the in-vehicle terminal device makes a collision determination to determine whether or not the own vehicle has a high collision risk with the pedestrian; that is, whether or not the own vehicle is highly likely to collide with the pedestrian, and provides an alert to the driver in the vehicle when it is determined necessary from the result of the collision determination.
Generally, in order to alert a driver, a warning sound or a warning voice announcement is produced or a warning image is displayed on a display device. However, such an alert alone is not sufficient for a driver to instantly grasp where a pedestrian with a high collision risk is located and which pedestrian around the driver's vehicle has a collision risk. Thus, there is a need to indicate the presence of a pedestrian with a significant collision risk on a display screen.
Such prior art technologies concerning the notification to a driver of the presence of a pedestrian with a collision risk include a pedestrian detection system including an in-vehicle display device configured to produce a map on which the locations of pedestrians are indicated with marks having different colors or shapes which are determined depending on the degree of risk (See Patent Document 1). Known technologies further include a device configured to notify a driver of the presence of a pedestrian with a collision risk by displaying an alert image projected on a windshield or using other display methods (See Patent Document 2).